Merge branch 'selftests/bpf: Various sockmap-related fixes'

Michal Luczaj says:

====================
Series takes care of few bugs and missing features with the aim to improve
the test coverage of sockmap/sockhash.

Last patch is a create_pair() rewrite making use of
__attribute__((cleanup)) to handle socket fd lifetime.

---
Changes in v2:
- Rebase on bpf-next (Jakub)
- Use cleanup helpers from kernel's cleanup.h (Jakub)
- Fix subject of patch 3, rephrase patch 4, use correct prefix
- Link to v1: https://lore.kernel.org/r/20240724-sockmap-selftest-fixes-v1-0-46165d224712@rbox.co

Changes in v1:
- No declarations in function body (Jakub)
- Don't touch output arguments until function succeeds (Jakub)
- Link to v0: https://lore.kernel.org/netdev/027fdb41-ee11-4be0-a493-22f28a1abd7c@rbox.co/
====================

Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>